Photothermographic film generally includes a base material, such as a thin polymer or paper, coated generally on side with an emulsion of heat sensitive materials. Once the film has been subjected to photostimulation (exposed), for example, by light from a laser of a laser imaging system, the resulting latent image is developed through application of heat to the film.
Several types of thermal processor have been developed for heat developing exposed photothermographic film. One type employs a rotating heated drum having multiple pressure rollers positioned around a segment the drum's circumference to hold the film in contact with the drum during development. Another type slides the photothermographic film over flat, heated surfaces or plates. Still another type of processor, commonly referred to as a flat-bed processor, includes multiple rollers spaced to form a generally horizontal transport path that moves the photothermographic film through an oven. Regardless of the type, however, each of these processors typically heats the photothermographic film to a desired processing temperature for a desired duration, commonly referred to as the dwell time, for optimal film development.
Some types of photothermographic film have emulsions that produce gases as the film is heated during the development process. These gases include contaminants, such as fatty acids (FAZ), which may subsequently condense on “cooler” surfaces within the processor. These deposits can accumulate over time and can damage processor components, cause film jams within the processor, and cause visual defects in the developed image. Consequently, processors developing photothermographic films having these types of emulsions often require regular maintenance to address problems resulting from such contaminants, which can be costly and result in processor downtime.
In efforts to reduce such problems, one type of drum processor includes internal ductwork designed to direct gasses out of the processor before the contaminants can condense. The processor includes a hinged cover that can be opened to allow access to the heated drum and pressure rollers for removal of jams and service. To accommodate the opening and closing of the cover, the ductwork is routed through an opening along the hinge line that is sealed by a gasket which is compressed when the cover is closed. However, due to its location along the hinge line, the gasket can sometimes be cooler than other surfaces and, consequently, FAZ tends to condense and accumulate along the gasket. When the cover is opened, accumulated FAZ may loosen and be deposited within the processor. Additionally, over time, the FAZ build-up can restrict air flow through the duct which can result in FAZ condensing on the drum and rollers and heat gradients within the processor which, in-turn, can result in film jams, premature wearing of drum coatings, and image artifacts in developed film.
It is evident that there is a need for improving thermal processors, particularly drum type processors, to reduce problems associated with gaseous contaminants produced during development of photothermographic film.